Need advice...going lean over 5k rpm

[flat_6]

Here's the background. I bought my car last fall and it needed a rebuild as the rings were cooked from going lean on top end, but could not be seen as no AFR gauge.
So it is now rebuilt to 3.3L, new 964 cams from Andial, new rockers,valve guides, recut valve seats, etc. It has Andail racing intercooler and Garrett GT3582R turbo set to 0.8 bar. I also install a Innovate AFR gauge.

Here are the 2 problems:

• Start the car cold, the idle is 400 rpm and sputters on acceleration. Once warm its spot on with 1000 rpm idle. Why poor when cold?

• Next and main problem. AFR is 14.6-14.8 off boost and 11.2-12 on boost until 5k rpm then it start to lean out quick. Soon as I see AFR of 13 I lift off and this depends on the ambient air temp but this week has been around 5300 rpm when starting to get these AFRs ??

Is my WUR the issue? My mechanic has said that someone has been monkeying with the fuel pressure regulator and is the reason for the poor cold starts.

Your advice would be great. Thx.

[xbmwguy]

thank god you got the afr guage or you would be doing it again . that turbo needs fuel up top. i would highly recomend a brian leaske adjustable warm up regulator in conjunction with a moddified fuel head from larry at flowtech. this will save your motor and keep you having fun at higher rpms

[JFairman]

What is the AFR gauge saying during the 400 rpm, sputtering cold start?
The rest of your AFR's sound normal for stock CIS.

Frank is right and that'll cost around $1000 with shipping if you do the work yourself.

or...

You could sell all the old CIS and distributor ignition stuff and switch to versatile and tunable EFI and crankfire ignition and the results may blow your mind . . .

[flat_6]

Definitely cant go EFI, would love to but the obvious $$$$
If I get the BL WUR and leave the current fuel head will that work?

Also, I have read on BL WUR and I am unsure about the RPM clamp. I see the benefits when driving flat out to pick an rpm to trigger the fuel enrichment, but I am finding during regular driving that i am not always on boost in the higher rpms are I may be holding my speed. Does this rpm clamp work inline with the map sensor to trigger the enrichment?

Thanks for the feedback so far guys!

[flat_6]

JFairman, the AFR is reading 13-15 range when idling at 400 rpm.

[RarlyL8]

Cold start issue is likely high cold pressure.

Lean boost issue may be fixed with an adjustable WUR and rpm switch. We handle those if interested. Cold and warm pressure is also adjustable on those units.

You won't know if you need a modified fuel head until the WUR pressures are adjusted and AFR data collected. I've seen too many folks with modded fuel heads that don't need them; we rebuild them back to OEM and all is well. We also handle OEM and modified fuel heads and have them in stock.

EFI is great if DIY, a potential nightmare if farmed out. $1000 for rebuilding the fuel head and WUR and you get a great running engine capable of 21mpg and 400WHP or spend $10,000+ and maybe a year later you get your car back and it runs like **** and never gets sorted out properly as only one shop can do it. DO a LOT of homework if even considering EFI.

[flat_6]

Thanks Brian, I did get a quote from you on the WUR. Can you answer my question about the rpm switch?

[heliolps2]

I think what going on with your cold start is that you most likely have the vacuum hose or hoses plumed incorrectly , what is happening is that your get vacuum on the retard side to your disribulator and what that does is retards your trimming and causes the low rpm when cold , as for you going lean on top ,it could be that your system pressure is to high , that is easily adjusted by removing or replaceing the shims with thinner ones one the fuel head , you will need CIS test gauge , the other thing you should check is the voltage going to the fuel pumps , as these cars get older the wiring get weaker , and cause low voltage and what would happen you run out of fuel on top,

[heliolps2]

[heliolps2]

[flat_6]

What should the fuel pump voltage be? 12v ?A
I will double check the vacuum lines.

Still want to understand if the BL rpm switch works inline with the map sensor? Does it trigger full boost enrichment from the set rpm on, regardless if there is boost or not?
I much not be understand this correct, please help me understand.

[Tt surgeon]

I would listen to Brian on this one.

[mooney265]

Originally Posted by flat_6

What should the fuel pump voltage be? 12v ?A
I will double check the vacuum lines.

Still want to understand if the BL rpm switch works inline with the map sensor? Does it trigger full boost enrichment from the set rpm on, regardless if there is boost or not?
I much not be understand this correct, please help me understand.

Brian could better answer that. But, I have one, so I'll take a go at it: the rpm switch "DELAYs" the full enrichment that would otherwise come too early in the rpm band. You can choose when to "delay" by choosing different rpm pills [ie 4000, 4500, 5000 etc]

Hope that helps...

[RarlyL8]

Yes that is the effect.
The WUR will dump fuel starting at ~0.3bar causing the midrange to be very rich. The RPM switch is plugged into the vac/boost port of the WUR and blocks that signal until the predetermined RPM is reached. You set that RPM based on where the fuel dump starts and then leans out on the AFR graph of your engine. By holding off enrichment you can smooth the midrange gaining torque and wasting less fuel. The top end adjustment is independent.

[heliolps2]

Ok , try this , before you start your car when it cold pull the vacuum hose off the dizzy , pull the one closest to the center of the engine, then start the car , the rmps should be at 1200 to 1000 rmps , if that happens the you know that we are on the right track, I had 6 other 930 at my home with the same problems they start and drive fine now. Call me any time 210-473-7158 Helio

[flat_6]

You guys are awesome. Thx.
Brian, I will be calling you Monday to order a Adj. WUR and rpm switch.
Do I need any other info from my car first?

[beepbeep]

930 motor with stock cams has such atrocious VE at high RPM's that slight leaning on the top isn't really such a issue that one might think.

Factory knew this and made it run rich where VE (and thus torque) is highest. At 6000 RPM, turbo is trying to cram air into cylinders but it just cannot do it well, due to port size and cam timing. I know many look at stock AFR's and think "ooh, it goes so fat in the middle and then leans out" but if you look at torque curve (and corresponding cylinder pressures) you see that it goes fat when it has to.
If it's going to ping, it will mostly do it at 4000-5000 RPM.

P.S. Change cam timing and/or intake/exhaust tuning and it all goes out of the window.

[flat_6]

Helio, I pull off the vacuum line you suggested and you are right. It idles at 1000-1200 rpm.
Hooked it back up and back to 500 ish.
Now what?

[heliolps2]

Give me a call 210 473 7158

[RarlyL8]

Goran/Beep has a good point and you do want to keep the midrange more fat than the top end, which is easy to do given the characteristics. I like low to mid 11's in the midrange and 12 at redline.

Helio's vac line swap does work, however if your engine used to run good when cold and now does not you need to fix that problem first before swapping vac ports.